Float valve for drill pipe and the like



Dec. 4, 1962 J. s. TAYLOR, JR 3,066,693

FLOAT VALVE FOR DRILL PIPE AND THE LIKE Filed Feb. 18, 1960' 2Sheets-Sheet l gllmflq NIMH |I ZJMM/ ATTORNEY DeC- 4, 1962 .1.5. TAYLOR,JR 3,066,693

FLOAT VALVE FOR DRILL PIPE AND THE LIKE Filed Feb. 18, 1960 2Sheets-Sheet 2 /Z /6' 4* A' f6 j?. 6'. 5 .a5 6* I/Z /s- 3 28 3 61- Z5 60/a 597/? '53 "a 34 5 y 22 JwIQZ 6 /2 '57 4|! 5 ,3 AT rxV D' a4 m Z4 23sa 3d "33 3/ 53 24 ze /5 l 25 5%' 8 48 4/ 52 5/ O I 6( 4Z 33 27 3/ @302gf3/W4? f5 4;

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United States Patent Gil-ice dhii Patented Dec. 4, i952? 3,666,693 jFLAT VALVE FR DRILL PEPE AND THE Ll'ii. .luiian S. nEaylor, Jr.,Milwaukee, Wis. (li-ld E. Northrop Drive, Midwest City, Ghia.) FiiedEen. i8, i969, Ser. No. 9,45%2 6 Claims. (Ci. i37-454.2)

This invention relates to back pressure valves, and particularly tothose of a type commonly known as drill pipe iioats, in that they areused in the drill pipe of a rotary drilling rig, the function of suchvalves being in etfect to` float the drill pipe in the fluid in the borehole during running into and out of the drill pipe, thereby relievingpart of the strain on the derrick and rig equipment. Such valves arealso useful for preventing blowouts of formation pressures through thedrill pipe, and for preventing a plugged bit when running the drill pipeinto the bore hole. They also prevent gushing of the well fluid from theupper end of the drill pipe and wetting the drilling crew and surfaceequipment.

While such valves are to perform these and other important functions,they introduce many problems, such as impe-ding tlow of the drillingfluid. The valves are also objectionable because of erosion of the partsby the drilling fluid; leakage under back pressure; failure to closeproperly; diflculty of passing and retrieving tools, particularly whendrilling with air and gas iluids; difiiculty in providing parts of amplesize and strength within the restricted limits of the drill pipesuiicient to withstand the rigorous service to which such valves aresubjected; exposure of vital parts of the valve to the drilling fluid;oscillation of the valving element; and other reasons that result infailure of such valves.

The present invention is, therefore, to provide a back pressure valvestructure that eliminates these. and other difficulties.

Other objects are to provide a back pressure valve of the apper type togive less restriction to the drilling iiuid, to allow passage andretraction of various tools and instruments that may be used in thedrill pipe; to provide a structure wherein the dapper hinge is locatedout of the flow of drilling fiuid, protected from erosion and shelteredby the i'lapper; to provide a structure which results in stronger, moresecure mounting with larger pivotal elements; to provide a structure inwhich the iiow of drilling fluid retains the ilapper in a generallyfixed open position and prevents oscillation thereof; to provide aiiapper which deflects the drilling liuid in a manner to reduce wear anderosion of the apper; and to provide a resilient support of the flapperto permit self adjustment of the flapper on its seat and yet provide forfreedom of movement of the hinge element.

It is also an object of the invention to provide the flapper with meansto indicate visually the extent of wear on the apper that is caused bythe drilling fluid and when the wear reaches a point when the tlappershould be replaced.

In accomplishing these and other objects of the invention hereinafterpointed out, i have provided improved structure, the preferred forms ofwhich are illustrated in the accompanying drawings, wherein:

FIG. l is a vertical section through a portion of a string of drill pipeillustrating a back pressure or float valve embodying the features ofthe present invention and showing the valving element in ope-n positionresponsive to ilow of the drilling fluid.

FIG. 2 is a similar view showing the valving element in closed positionto prevent back ow through the drill pipe, as when shutting off backpressure and when lowering the drill pipe into the bore hole.

FIG. 3 is a similar view showing a modied form of valving elementadapted to be retained in open position during lowering of a tool or thelike through the valve.

FIG. 4 is an enlarged perspective view of parts of the back pressurevalve, shown in disassembled, spaced relation to better illustrate theconstruction thereof.

FIG. 5 is a horizontal section through the back pressure valve taken onthe line 5--5 of FIG. l, particularly showing offset of the passagethrough the valve.

FlG. 6 is an enlarged section through the seat portion of the backpressure valve, showing the valving element or flapper in open position.

FIG. 7 is a similar view showing the valving element or flapper inclosed position.

FIG. 8 is a section on the line 8 8 of FIG. 7 to illustrate mounting ofthe hinge pin.

FGS. 9, 10 and il show fragmentary sections of a flapper valve,illustrating modified means for visually indicating wear caused byerosion of the drilling iiuid.

Referring more in detail to the drawings:

1 designates a portion of a string of drill pipe, such as used in rotarydrilling of a bore hole. The string of drill pipe is made up of standsof pipe connected together by pin and box joints 2 and 3. The lower endof the drill pipe carries the drill bit (not shown), and the upper endis connected with a kelly (also not shown) that provides a connectionbetween the drill pipe and the rotary turntable of the drilling rig bywhich the drill pipe is rotated to rotate the bit. The Kelly rod isconnected with a swivel head through which a drilling fluid is suppliedunder pressure for circulation downwardly through the pipe for dischargethrough the bit to carry the cuttings to the top of the bore hole, as inthe usual rotary drilling practice.

As the bore hole deepens, additional stands of pipe are added betweenthe Kelly rod and the uppermost section of pipe. The weight of the drillpipe increases with the addition of each stand of drill pipe, and indeep drilling the weight of the drill pipe places the drilling rig anddrilling equipment under severe strain, particularly when running thesections of pipe into the bore: hole, when it becomes necessary tochange bits or to perform other operations incidental to rotarydrilling. To avoid this difculty and reduce the load on the derrick andother surface equipment, most drill pipes are equipped with a backpressure or oat valve that may be located at different elevations in thedrill pipe, usually in parts thereof close to the drill bit, although insome instances if the main use is to eliminate back pressure, suchvalves may be located near the upper end of the drilling string. In anyinstance the valve is to act as a check valve to prevent blowoutsthrough the drill pipe and to serve as a float and to prevent gushing ofthe well fluids through the upper end of the drill pipe when the drillpipe is being lowered into the bore hole and to allow passage of thedrilling fluid to the drill bit when drilling.

The back pressure valve of the present invention is generally indicatedby the numeral i and includes a body member 5. The body member comprisesan upper cylindrical portion d and a lower cylindrical portion S that isconnected therewith by bar portions 9. The upper portion 6 is to carryseals with the bore of the drill pipe and to provide a seat for avalving element or flapper valve 10. The lower portion 8 cooperates withthe bar portions 9 to provide a cage ll (FIGS. l to 4, inclusive) inwhich the valving element or flapper valve lil is adapted to operate.

It is obvious that the inner diameter of a drill pipe is limited insize, and a back pressure valve inserted therein is a restriction to theflow of the drilling fluid, and particularly when the parts of the valveare of a size to be sufficiently strong to withstand the ruggedconditions under which such valves must operate. When the parts are ofsmall size they are too fragile to stand up under service. This isparticularly true of the hinge pin 4S and mounting therefor where alapper type of valving element il) is used, as in the case of thepresent invention, because a tlapper offers less restriction to the flowand functions better under abrasive conditions.

In carrying out the present invention and to avoid this diiiiculty, theflow passage 12 through the portion 6 of the valve body is offsetlaterally from the rotary axis of the drill pipe, to leave on one sidethereof a wall portion 13 only of suicient thickness to adequatelyaccommodate the annular grooves i4 for containing packing rings 15, sothat the opposite diametrical side has a substantially thick wallportion 16 to provide the material necessary to mount the hinge pins 43of ample size to support the valving element it) and to protect thevalving element when in open position. ln this way, a wall portion 16 ofample thickness is provided with an adequate flow passageway 12 (FIG.5). To facilitate the flow from the rill pipe into the inlet of thepassageway f2, the upper end of the portion 6 is flared or funneled asindicated at i7. The lower end of the body portion 6 has a at face 13surrounding the outlet of the passageway i2 to provide an annular seatportion immediately encircling the outlet or port 19.

The body member 5 may be of a diameter to slide freely within the axialbore of the drill pipe part or section in which it is inserted becauseof the seal effected by the packing rings 15 and of the clamping actionon the ends of the body member 5 between an internal annular shoulder 26and the end 2l of the pin 2 (FIGS. l, 2 and 3).

As above stated, the valving element is of the flapper type andcomprises a disk shaped body having a generally at face 22 and asomewhat coned opposite face 23 to provide the thickness of materialnecessary to accommodate a flow directional recess 24 within the flatface 22 of the valving element. The hinge point of the valving elementis located above the seating face i8 and within the lower part of therelatively thick wall portion 16 (FIGS. 6, 7 and 8). Therefore, the diskshaped body of the valving element or iiapper valve 1li has a radiallyextending arm portion Z5 carrying a lug portion 26 that extendslaterally from the arm portion 25 above the seating face i8. The lugportion 26 is shaped to provide ears 2.7 and 23 having a recess 29therebetween to accommodate a spring 36, later to be described (FIGS. 4,5, 6, 7 and 8). The ears 27 and 28 have generally circular face portions31 to t within the circular portion 32 of a recess 33. The recess 33extends upwardly from the seating face f8 and inwardly of the outer faceof the wall portion i6, as best illustrated in FIGS. 4, 5, 6 and 7. Therecess 33 is of a width to accommodate the ears 27 and 23 therein andthe facing sides 34 thereof are substantially flat to contact the outerside faces 35 of the respective ears, as shown in FIGS. 4 and 8.

Aligning axially within the recess 33 are recesses 36 and 37 spacedtherefrom to leave ears 3S and 39 having axial bores 40 and 4l toaccommodate therein resilient bushings 42 and 43 (FIGS. 4, 5 and 8). Thebores 40 and 41 have the midportions of larger diameter to key taperedperipheries of the bushings therein, as best illustrated in FIG. 8. Theresilient bushings 42 and 43, therefore, tit snugly and tightly withinthe bores 40 and 41 of the ears 33 and 39 and have axial openings 44 and45 (FIG. S) registering with axial openings 46 and 47 in the ears 27 and23 of the valve element for passing therethrough the hinge pin 4S. Thehinge pin 48 fits tightly within the bores 46 and 47 of the ears 27 and28 so that it turns with the valve, but the end portions 49 and 50 (FIG.8) of the hinge pin turn freely within bearing sleeves 51 and 52 thatare bedded within the resilient bushings 42 and 43, the sleeves 51 and52 being preferably of nylon or Teflon material.

It is thus apparent that the ends 49 and 56 of the hinge pin 43 arereiliently supported in the ears 38 and 39 by reason of the resilientbushings 42 and 43. The resilient eases bushings and 43 are importantfor cushioning the pound and shock forces, caused by impact of highvelocity fiuid turbuiently moving past the dapper when in open position.Without protection by the bushings of the vital pir/etai points fromshock forces, the useful life would be short, because the hinge pin andlugs 27 and 28 on the valving element or dapper valve llt) would soonpound out, but with the resilient bushings the useful life of the partsis increased indefinitely. The sleeves 51 and '232 inside the resilientbushings 42 and 43 reduce rotational friction between the pin 48 andbushings, so that the pin turns freely to allow for free action of thevaiving element or dapper valve itl.

The spring 317' is adapted to normally hold the valving clement orflapper valve l@ in closed position, and includes a coil portion 53 thatis mounted on the hinge pin within the recess 23 and the ends of thecoil portion iinate in arms 6d and 55 that respectively engage in groovein the body member 5 and in a groove 57 in the outer side 23 of thefrapper valve, as illustrated in 6 and 7. The groove S6 extends upwardlyfrom the recess 33 at a point between the ears 33 and 39, as cest shownin FIG. 4.

The face portion 23 above the horizontal diameter of the llapper isrounded transversely as indicated at 38 to substantially conform to thecurvature of the drill pipe, so that the drill pipe forms an abutmentfor the valving element or dapper valve 16 to hold the valving elementor ilapper valve 1G with the face 22 thereof in slightly inclinedposition relatively to the longitudinal axis of the valve, as shown inFIGS. l and 6. This is desirable to prevent the flapper it) from oscillting. By having the drilling fluid irnpinging on the slightly inclinedface 22 of the vaive, the fluid under iiow will continuously hold theiiapper it? in an open position, opposing the action of the spring 3o.The inclined apper surface 23 in the open position acts to urge theflapper to the closed position by counterow in the event of springfailure. The indentation or recess 24 serves as a hydraulic deiiectionsurface to protect the valve from abrasion (FGS. 6 and 7).

ln order to supplement seal between the seat 18 and face of the valvingelement or frapper valve 10 and, in fact, provide the principal seal,the peripheral portion of the face 18 has an inwardly extending annulargroove 59 of dovetail cross section for retaining an annular sealingring 6i) which is of resilient material to make resilient contact withthe flat face 22 of the valving element or flapper it?. The groove isalso vented through ports 61 to allow passage of any iluid trapped underthe sealing ring 69. These ports are important to prevent the trappedliquid from popping the ring 6) out `of the groove 53 and being cut offby the flapper.

Wear on the seating face 22 of the valve is critical and should notexceed an amount of %4 inch, therefore, when the wear approaches thisamount the valve should be replaced. The wear on the valving element ordapper valve 1t) is not always discernible -to the usual driller, and,therefore, to avoid the necessity of actual measurenient, the lipportion 62 of the valve is provided with a transverse groove or notch 63(FIGS. 6 and 7), for example, 9764 inch deep on the seating face sidethereof, so that when the wear tends to `obliterate the notch 63 thevalve should be replaced. FIGS. 9, l0 and ll show different ways ofproviding other types of a visual wear indicating means for determiningthe amount of wear. In FG. 9 the lip of the valve is provided on theunder side with a transverse groove 64 to leave a lip portion 9754 inchthick, so tha-t when it is substantially worn off the valve should bereplaced. In FIG. l() the peripheral edge of the valving element orflapper valve lil has an intermediate groove 65 to leave a lip portionon the seating face of the valve 32H inch thick. In FIG. 1l, theindicating means comprises a hole 66 that is drilled from the face side23 into the material of the valving element or dapper valve, toterminate 1%4 inch from the face 22, so that when the wear is sufficientto expose the hole 66, the valve should be replaced.

Notches 67 in the portion 6 of the valve body accommodale a centeringdevice for a deviation indicator (not shown).

The valving element or dapper valve illustrated in FG. 3 has a loop 68fixed to the face thereof to be engaged by a tool 69 that is to belowered through the drill pipe. The loop 63 is also adapted to engagethe cable '7d to hold the valving element or dapper valve 1d open duringlowering and lifting of the tool 69. The loop 66 is preferably of springmaterial and is suitably fastened at the ends to the face of the valve.

The back pressure valve may be installed at a desired position in astring of drill pipe I1, however, it is usually inserted at a low point,for example, in the stand of pipe to which the drill bit is connected orin a short section of pipe having the shoulder` which is insertedbetween the lower stand in the drilling string and the pin 2 of thedrill bit, in which case the body member 5 is rigidly retained fromaxial movement between the shoulder 20 and the end face 2l of the pin 22and is itself coaxial with the bore of the drill pipe, but the axis ofthe dow passage 12 therein is odset, as shown in FIG. l. During loweringof the drill pipe through the bore hole, the valviru7 element or dappervalve l0 is held in closed position by the action of the spring 3d, sothat the drilling duid in the well does not gush upwardly and escapethrough the upper end of the drill pipe.

When the drill bit reaches the bottom of the hole and the drilling duidis circulated through the drill pipe, the valving element or dappervalve opens against the action of the spring 30, that is, the valvingelement or dapper valve l0 is moved downwardly and outwardly from itssealing contact with the O-ring 6d under pressure of the dri-lling duiduntil the portion 58 of the dapper valve engages the wall of the portionof the drill pipe in which the valve has been located. In this position,the dat face portion 22 of the dapper valve slopes downwardly andinwardly for sudicient impingernent of the drilling duid thereon to holdthe dapper valve in open position during the time that the drilling duidis in circulation. It will be noted that the portion of the drillingduid impinging in the recess 24; is dedected thereby and out of contactwith the dat portion of the valve that makes contact with the O-riug 6d,so that abrasive material in the drilling duid does not tend to wear thevalving element or dapper valve itl at the points where a seal iseffected when the valving element or dapper valve is closed. When thevalving element or dapper valve it) is being held in open position, itis located under and protected by the relatively thick portion 15 of thebody member. It is also to be noted that the hinge pin 43, spring 3?,and bushings 42 and d3 of the hinging elements are located out of thepath of the drilling duid, therefore, they are not subject to cloggingand/ or cutting by the solids carried with the drilling or pressureduid.

While the pressure duid moves with substantial turbulence across theface of the valve, the shocks imparted thereby are absorbed by theresilient bushings 42 and 43 and, therefore, the hinge pin 4d and hingeears 27-28 and 38-39 are not subject to pounding out, consequently theyhave a substantially long life.

lt is also obvious that the resilient bushings provide a yieldablepivotal axis for the dapper valve, to assure positive seating thereofwhen the dapper is closed, as when doating in the drill pipe, and forexcluding the drilling duid that is in the bore hole from passingupwardly into the bore of the drill pipe. The yieldable axis alsoassures positive seating of the dapper valve in case of a blow-backpressure acting upon the dapper valve,

in case of a blowbaclt resulting from high pressure in the formationthrough which the bore hole is drilled. the valving element or dappervalve It) will act as check. That is, the pressure will act, togetherwith the spring, to

close the valve and block off the high pressure from blowing out throughthe drill pipe. When the valve is in closed position, the seating faceof the dapper valve makes sealing contact with the O-ring 50 to assurethat the high pressure does not pass the valve.

Another feature is that pressure cannot accumulate behind the O-ring,since any leaking pressure around the ring is vented through the ports6l.

When the string of drill pipe is removed, the dapper valve may beinspected for wear by observing the depth of the notches 63. When it isnoted that the notches d3 have been obliterated, then the dapper valveshould be removed and replaced with a new dapper valve.

The sleeves S1 and 52 are also an important feature of the invention inthat while the bushings prevent pounding out of the hinge pin andrelated parts, the hinge pin rotates freely within the bearing sleeveswhen swinging to and from closed position.

When drilling with air or gas under pressure and tools are to be loweredthrough the drilling string by means of a cable, the back pressure valveis usually located near the upper end of the drilling string, in whichcase a valving element or dapper valve iti may be used having the campart 68 as shown in FIG. 3 to hold the valve element open `by engagementthereof with the cable 7d. Otherwise the construction and mounting ofthe valving element it) is the same as that illustrated in the firstform of the invention.

From the foregoing it is obvious that l have provided a dapper typecontrol valve wherein the parts are of rugged construction and arecapable of withstanding the forces to which they are subjected, allwithout materially obstructing dow through the drill pipe.

What is claimed and desired to be secured by Letters Patent is:

l. A valve for controlling dow of duid through a string of drill pipecontained vertically in a bore hole, said valve including a body memberadapted to dt within the drill pipe and having a dow passagewayextending vertically ltherethrough and having an annular seat encirclingthe lower end of said passageway, a dapper valve having a seating faceand having hinge means, a hinge pin fixed to the hinge means and havingbearing portions on opposite sides of the hinge means, resilient bushingmeans carried in spaced apart relation in the body member transverselyto the dow passageway at a point above said sent on the exterior sidethereof for resiliently containing the bearing portions of the hinge pinto hinge the dapper valve on a yieldable transverse axis above saidannular seat and laterally of the dow passageway to prevent pound out ofthe hinge pin under impingement or the 'duid upon the seating face sideof the dapper valve when an open position, and resiliently yieldablemeans for retaining said dapper valve in a closed position with theseating hse thereof in contact with the annular seat, said retainingmeans `being yieldable responsive to pressure of the duid upon saiddapper valve to move the dapper valve downwardly and laterally from `theannular seat to said open position with the seating face of the dappervalve sloping downwardly and inwardly for sumcient impingernent the duidthereon to hold the dapper valve generally lixed in said open positionduring dow of said duid. said seating face of the dapper valve having arecess portion within said seating face, said recess being of a shape toprovide an hydraulic surface for dedecting said duid from saidsurrounding seating face of the dapper valve to reduce wear of saidsurrounding seating face by said inipingcment and abrasive action of theduid.

2. A valve for controlling dow of duid through a string of vertical pipecontained in a bore hole, said valve including a body member adapted tolit within the pipe and having a vertical dow passageway extendingaxially therethrough and having an annular seat encircling the lower endof said passageway, a dapper valve having a seating face and havinghinge means, a hinge pin dxed to the hin mems and having bearinfyportions on opposite sides of annesse the hinge means, resilient.bushing means carried in spaced apart recesses in a bore of the bodymember eA lrc e transversely to the flow passageway at a point abovesaid seat and on the exterior side thereof for containing the bearingportions of the hinge pin to hinge the dapper valve on a yieldabletransverse axis above said annular seat and laterally of the llowpassageway to prevent pound out of the hinge pin under impingement ofthe lluid upon the face side of the llapper valve when in an openposition, and means for retaining said dapper valve in a closed positionwith the seating face thereof in contact with the annular seat, saidretaining means being yieldable respon sive to pressure of the duidilowing downwardly through the passageway and against said flapper valveto move the dapper valve downwardly and laterally from the annular seatto said open position with the seating face of the dapper valve slopingdownwardly and inwar ly for in suliicient impingenient of the uidthereon to hold the dapper valve generally fixed in said open positionduring ilow of said `fluid, said apper valve having recess portionsurrounded by said seating face thereoland ld recess portion being of ashape to provide a hydraulic sur for deliecting said luid from saidsurrounding seating face to reduce wear of the seating `face of thedapper valve, and said seating face having means to indicate visuallythe wear that may occur on said seating face.

3. a valve for controlling flow of iluid through a string of verticalpipe contained in a bore hole, said valve including a body memberadapted to fit within the pipe and having a vertical ow passagewayextending axially therethrough and having an annular seat encircling thelower end of said passageway, said seat having an annular groove, aresilient ring in said groove, a dapper valve` having an annular seatingface and having hinge ineens, a hinge pin fixed to the hinge means andhaving bearing portions at the ends thereof, spaced apart, resilientbushing means carried in the body member transversely to and offset fromthe flow passageway at a point above said seat on the exterior sidethereof for containing the bearing portions of the hinge pin to hingethe llapper valve on a yieldable transverse axis above said annular seatand laterally of the llow passageway to prevent pound out of the hingepin under turbulent action of the fluid upon the dapper valve when in anopen position, and rneans for retaining said flapper valve in a closedposition with the seating face thereof in sealing contact with theresilient ring, said retaining means being yieldable responsive topressure of the fluid upon said ilapper valve to move the i'lapper valvedownwardly and laterally from the annular seat to said open positionwith the face of the llapper valve having the annular seating facesloping downwardly and inwardly for sucient impingernent of the lluidthereon to hold the ilapper valve generally fixed in said open positionduring ow of said iluid, said face of the flapper valve having a recessportion of a shape to provide an hydraulic surface for deflecting saidfluid from said annular seating face of the ilapper valve to reduce wearof said annular seating face by abrasive action of the lluid.

4. A float valve for controlling flow of high pressure liuid through avertical string of drill pipe. said lloat valve including a cage havingan upper cylindrical portion roviding a sealed t when the float valve isnio. nted within the drill pipe and having a transverse lower tace, saidupper cylindrical portion having a vertical passageway extend* ingthrough said transverse face on an axis ollset laterally from the axisof the upper portion of the cage to provide -a thick-walled portion atone diametrical side, said transverse face having an annular seatconcentrically encircling the passageway, a dapper valve having a seatfor engaging said annular seat of said upper part of the cage forclosing the passageway, said thick-wall portion having a recessextending upwardly from said transverse face on the outer side of saidannular` seat and opening or through said thickwalled portion, saidthick-wall d tion also having axially aligned transverse bores atopposite sides of said recess and located above annular seat, resilientbushings itting tightly within the bores, bearing sleeves bedded withinsaid resilient bushings, spaced apart ears projecting at substantiallyright angles from the seating face of the dapper valve and into saidrecess, a hinge pin fixed within said ears and having ends journaled toturn within the bearing sleeves to provide a hinged support for thedapper valve having a width approac' ng the diameter of the iiappervalve and to forni a axis above said annular seat, means for normally rethe dapper valve in closing relation with said passaeeway and yieldablyresponsive to the pressure 'duid when dei L, through the passageway,said dapper valve being inovable downwardly and laterally from saidannular sea. y the ears swing about said hinging axis and into saidrecess to carry the apper valve to an open position subst ntially out ofthe llow issuing through said passageway, v back of the llapper valve incontact with the drill e to support the seating side of the flappervalve in a wardly sloping position for suilicient impingernent thepressure fluid thereon to hold the llapper valve substen tiallyimmovable in said open position.

5. A iloat for controlling llow of high pressure iluid through avertical string of drill pipe, said tloat valve including a cage havingan upper cylindrical portion providing a sealed lit when the oat valveis rnou .ted within the drill pipe and having a vertical passa ev'ayextending through a transverse lower face, said transverse face havingan annular seat concentrically encircling the passageway, a flappervalve for closing the passageway and having a surrounding seating facefor engaging said annular seat of said upper part of the cage, means forhinging the llapper valve to the upper cylindrical portion of the cageat one side thereof to swing on an axis located above Said transverseface from `a position closing the passageway to an open position withthe seating face of the dapper valve sloping downwardly and inwardly forsufficient impingement of the iiuid thereon to hold the `frapper valvegenerally xed in said open position during ow of the uid, and the saidllapper valve having a shape inside the seat thereof to provide ahydraulic surface for deilecting said fluid away from said surroundingface to minimize wear on said surrounding seating face of the llappervalve by said impingernent and abrasive action of the fluid.

6. A float valve for controlling llow of high pressure huid through avertical string of drill pipe as described in claim 5, and wherein theseating face i, te indicate visually the wear that may occur on saidseating face.

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